a floating-point number with a value in the range 0.0
- to 1.0, indicating the relative 'quality' of this variant
+

a floating-point number with a value in the range 0[.000]
+ to 1[.000], indicating the relative 'quality' of this variant
compared to the other available variants, independent of
the client's capabilities. For example, a jpeg file is
usually of higher source quality than an ascii file if it